Prior Art
The invention is based on a network interface of for a serial bus having at lest two bus lines. A network interface is already known from DE-OS 38 26 774. The network interface described there is designed for use in the so-called Controller Area Network (CAN). The CAN is a serial bus system which is primarily designed for use in motor vehicles. In this case, the information is transmitted between a plurality of network subscribers via a two-wire link. Each network subscriber contains a network interface. Each network interface is connected to the two-wire link. Each network interface has a differential receiver whose inputs are linked to the two-wire link. In the event of one of the two signal lines failing as a result of a short-circuit or interruption, two-wire reception is no longer possible. The network interface according to DE-OS 38 26 774 is designed such that it recognizes error states of the above type and then switches over from two-wire reception to single-wire reception. For this purpose, it applies a fixed terminal potential to one input line of the differential receiver. If differential reception is possible again subsequently to this, the terminal potential remains connected to the input line and information reception takes place via the remaining signal line. In other cases, the terminal potential is applied to the other signal line and the terminal potential is disconnected from the first signal line. After this, information reception can take place via the other signal line. In both cases, the same terminal potential is applied to the respective signal line. The terminal potential in this case corresponds to the comparator mid-potential. When the network interface is in single-wire operation, common mode interference resulting, for example, from an earth offset between two network subscribers, cannot be completely suppressed. The permissible earth offset is governed by the voltage difference between the terminal potential and the recessive bit level on one of two signal lines.